JP5173978B2 - Smudge inspection device for document reading unit, image forming apparatus, and method for soiling inspection of document reading unit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading unit stain inspection device , an image forming apparatus, and a document reading unit stain inspection method, and more particularly to a document reading unit stain inspection device used for shading inspection, a copying machine, a facsimile machine, and a multifunction machine ( The present invention relates to an image forming apparatus such as an MFP (Multi Function Peripheral), and an improvement in a method for inspecting a stain on a document reading unit .

  Conventionally, this type of image forming apparatus rotates based on image data read from a CCD (charge coupled device) sensor by irradiating light on a document or image data read from a contact type sensor such as a CIS (contact image sensor). A latent image is formed on the surface of the photosensitive member, a toner image is formed from the latent image with toner supplied from a toner cassette, the toner image is transferred to a conveyed sheet, and the toner is transferred to the sheet through a heat fixing unit. A configuration in which the sheet is heated and fixed and discharged is well known.

  In addition, due to variations in components and functional causes, a shading phenomenon in which the density and luminance of image data for each line read from a CCD sensor or CIS sensor is not uniform is likely to occur, and CCD There is also a concern that dust or the like adheres to the sensor or CIS sensor surface and the same phenomenon occurs.

  In particular, in an image forming apparatus, during maintenance after shipment, image data obtained by reading a test sheet is displayed, and shading inspection is performed by determining whether a white line or a black line is generated on the display image. When a white line or the like is generated, the reading surface of the CCD sensor or CIS sensor is cleaned or the sensor itself is replaced.

  In particular, the CIS sensor is often used for reading the back side when reading on both sides, and is a sensor that reads an image in close contact with the surface of the document. Therefore, shading is likely to occur on the surface, and shading inspection is important. It is.

  Conventionally, as a shading inspection method, for example, a shading inspection method disclosed in Japanese Patent Laid-Open No. 2007-267078 (Patent Document 1) has been proposed.

  This patent document 1 is a shading inspection method for reading a band having a predetermined density on a test chart and detecting a line from the image of the read band. The first average value of pixels belonging to a target pixel column and the target pixel Calculating a second average value of pixels belonging to a plurality of columns in the vicinity of the column, and determining that the shading data is abnormal when the first average value is not within an allowable range from the second average value. The detection of the line is possible with the same margin both near the center and at the end.

JP 2007-267078 A

  However, in Patent Document 1 described above, as described in the specification, it is necessary to previously install inspection software on a personal computer externally connected to the image forming apparatus, and a personal computer is required for inspection. In addition, it is time consuming and the detection of white lines, color lines, and the like is likely to be complicated, and processing time is required. Therefore, there is room for further improvement in performing accurate shading inspection with a simple configuration.

  Moreover, when performing a shading inspection, it is possible to distinguish between smudges on the reading surface of the CCD sensor or CIS sensor and stains on the surface of the rotating photoconductor that transfers the toner image onto the paper, and identify which stains are distinct. There is also a need to do.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and can be implemented by being mounted on an image forming apparatus, and can be easily and surely checked for dirt on a document reading section . It is an object of the present invention to provide a stain inspection method for an image forming apparatus and a document reading unit .

In order to solve such a problem, a smear inspection apparatus for a document reading unit according to claim 1 of the present invention includes a document reading unit that optically reads a surface image of a fed document and acquires image data; A histogram is created when the read image data is a gray document, a threshold value for converting the image data from the gray document into a monochrome binary image is created from the histogram, and the image data from the gray document is converted based on the created threshold value. An image conversion unit that outputs a binary image obtained by converting the monochrome binary image into a black-and-white binary image and outputs the binary image obtained by re-inverting the monochrome binary image, and the converted monochrome binary image and the re-inverted converted binary image. And a printing section that prints as dirt inspection data of the document reading section .

According to a second aspect of the present invention, there is provided the apparatus for inspecting a smudge of a document reading section, wherein the document reading section has a contact-type reading sensor that contacts the document and reads image data.

According to a third aspect of the present invention, there is provided a stain inspection apparatus for a document reading unit , wherein the image conversion unit creates a monochrome histogram for image data of a read gray document.

An image forming apparatus according to a fourth aspect of the present invention includes the smear inspection device for the original reading unit according to any one of the first to third aspects, and includes an image forming unit that forms an image of the read image data. It is configured.

According to a fifth aspect of the present invention, there is provided a document reading unit stain inspection method , a document reading process for feeding a gray document and optically reading a gray image for inspection on the surface to obtain image data; A histogram creation process for creating a histogram from image data relating to an original, a threshold creation process for creating a threshold for converting image data relating to the gray original into a black and white binary image, and a gray original based on the created threshold Image data is converted into a black and white binary image and output, and at the same time, an image conversion process for outputting a binary image obtained by re-inverting the black and white binary image , the converted monochrome binary image and the re-inverted 2 And a printing process in which the value image is printed by the printing unit as dirt inspection data of the document reading unit .

According to a sixth aspect of the present invention, there is provided a method for inspecting a stain on a document reading unit, wherein the document reading process uses a contact-type reading sensor that closely contacts a document and reads image data.

According to a seventh aspect of the present invention, there is provided a document inspection unit stain inspection method in which the image conversion process creates a single-color histogram in the image data of a read gray document.

In the document reading unit stain inspection apparatus and the document reading unit stain inspection method according to the first and fifth aspects of the present invention, a gray document is fed and a gray image for inspection on the surface is optically read. Image data is acquired, a histogram is created from the image data relating to the read gray original, a threshold value for converting the image data relating to the gray original into a black and white binary image is created from the histogram, and the gray original is obtained based on the threshold value. Converts and outputs image data to a monochrome binary image, outputs a binary image obtained by re-inverting the monochrome binary image, and reads the converted binary image and the re-inverted binary image read from the original since printing by the printing unit as a part of the dirt inspection data, can be mounted to the image forming apparatus, after the simple and dirt test reliable document reading section is possible, white streaks also Or not the cause of the black stripe generated due to contamination of the image reading portion, or discrimination is also facilitated due to the image forming unit.

In the document reading unit stain inspection apparatus and the document reading unit stain inspection method according to claims 2 and 6 of the present invention, the document reading process is performed using a contact-type reading sensor that closely contacts the document and reads image data. It is easy to detect dust or the like that easily adheres to the surface of the sensor that reads an image in close contact with the document surface.

In the document reading unit stain inspection apparatus and the document reading unit stain inspection method according to claims 3 and 7 of the present invention, a histogram relating to a single color in the image data of the read gray document is created. Simple and accurate shading inspection can be performed.

1 is a block diagram showing an embodiment of an image forming apparatus equipped with a smear inspection device for a document reading section according to the present invention. It is a principal part block diagram which shows the principal part of the dirt inspection apparatus of the original document reading part which concerns on this invention. FIG. 3 is a diagram illustrating an operation panel unit of the image forming apparatus according to the present invention. It is a figure explaining operation | movement of the dirt inspection apparatus of the original document reading part which concerns on this invention. It is a figure explaining operation | movement of the dirt inspection apparatus of the original document reading part which concerns on this invention. 6 is a flowchart for explaining the operation of the smear inspection device for the document reading unit according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a document reading unit stain inspection apparatus , an image forming apparatus, and a document reading unit stain inspection method according to the present invention will be described below with reference to the drawings. It should be noted that the document reading unit stain inspection apparatus and the document reading unit stain inspection method of the present invention will be described in the course of describing the image forming apparatus of the present invention.

  FIG. 1 is a block diagram showing an embodiment of an image forming apparatus A according to the present invention.

  The image forming apparatus A includes a document reading unit 3, a storage unit 5, an operation panel unit 7, a printing unit 9, and a transmission / reception unit 11 with the main control unit 1 as a center, and constitutes, for example, a multifunction peripheral (MFP). . The image forming apparatus A has a configuration other than this, but since it is not the gist of the present invention, description and illustration are omitted.

  The document reading unit 3 is a scanner that optically reads the double-sided image from the automatically fed document 13 and generates image data as will be described later, and image data for each page under the control of the main control unit 1. Is stored in the storage unit 5. Details of the document reading unit 3 will be described later.

  The storage unit 5 stores read image data from the document reading unit 3 and received image data (to be described later) from the transmission / reception unit 11 under the control of the main control unit 1, and also reads and writes the operation program of the main control unit 1. Possible, for example, a hard disk.

  The operation panel unit 7 is arranged on the upper part of the main body case 15 shown in FIG. 2 (not shown in FIG. 2), and is known as a display unit capable of displaying various operation states under the control of the main control unit 1. It has a function as an input unit such as a liquid crystal display panel and a touch switch for receiving an operation instruction of the apparatus.

  For example, as shown in FIG. 3, the operation panel unit 7 is associated with various operation instructions and selection keys 7a such as printing (copying) processing, printer processing, scanner processing, facsimile transmission / reception processing, etc. In addition to the publicly known numeric keypad 7b, start key 7c, stop key 7d for inputting setting change of setting items, the display panel unit 7e for displaying the operation status of the apparatus is provided.

On the display panel unit 7e, an inspection start key 7f for starting a shading inspection on one side (front surface) of the document 13 and an inspection start key 7g for starting a stain inspection of the document reading unit 3 on the opposite surface (back surface) are arranged. ing.

The start key 7c can be used to execute reading of the document 13, and the stop key 7d can be used to input an instruction to stop reading of the document 13, and the inspection start keys 7f and 7g can be used to start the stain inspection of the document reading unit 3 .

  The printing unit 9 is arranged in the main body case 15 of FIG. 2, and although not shown in detail, a plurality of paper feeding units on which paper is set and the above-described image data are developed into print image image data from the toner cassette. A color or monochrome printing engine as an image forming unit having a transfer unit (rotating photoreceptor) that develops toner with toner and transfers a toner image onto a sheet, and a fixing unit that fixes a transferred image on the transferred sheet It is.

  The transmission / reception unit 11 in FIG. 1 is an interface unit that transmits / receives information such as various image data to / from an information processing apparatus B such as a computer via a network NT according to a predetermined protocol.

  The main control unit 1 includes a CPU, a ROM that stores an operation program for the CPU, and a working RAM (none of which are shown), and includes the document reading unit 3, the storage unit 5, and the operation described above. While controlling the panel part 7, the printing part 9, the transmission / reception part 11, etc., the function part (not shown) of the image forming apparatus A is controlled. Other functions will be described later.

  Next, the document reading unit 3 described above will be described with reference to FIG.

  In FIG. 2, transparent contact glasses 17 and 19 are arranged on the upper side of the main body case 15. The contact glass 17 has an elongated rectangular shape, and is in the main scanning direction of the document 13 to be read (perpendicular to the conveyance direction of the document). In the direction of the main body case 15.

  The contact glass 19 has a rectangular shape larger than the size of the document 13 and is disposed so as to extend in the direction opposite to the contact glass 17 from the vicinity of the contact glass 17.

  Inside the main body case 15, immediately below the contact glass 17, a line-shaped light source 21 made of, for example, a light-emitting diode that emits light toward the document 13 positioned on the contact glass 17, and the contact glass 17 side. A reading unit 27 is formed which includes a mirror 23 that receives and reflects the reflected light and a storage portion 25 that stores these mirrors.

  The reading unit 27 is connected to a moving unit 29 disposed inside the main body case 15. The reading unit 27 starts from a position immediately below the contact glass 17 and extends along the contact glass 19 in parallel to the right end in the figure. While moving intermittently at the timing, the moving part 29 is controlled to reciprocate so as to return toward the start when it reaches the end.

  In the main body case 15, mirrors 31 and 33, a condenser lens 35, and a first reading unit 37 are arranged on the optical axis of the reflected light from the mirror 23 to form an optical system.

  The first reading unit 37 is composed of, for example, a CCD sensor, is bent and guided by the mirrors 31 and 33, and is reflected at the level corresponding to the amount of light based on the reflected light from the reading unit 27 collected by the condenser lens 35. The image data converted into a digital signal is output to the calculation unit 39.

  The calculation unit 39 performs various filter processing calculations and processing operations such as enlargement / reduction on the digital image data from the first reading unit 37 and the second reading unit 51 to be described later, via the main control unit 1. The data is output to the storage unit 5.

  An automatic document feeder 41 is placed on the main body case 15 so as to cover the contact glasses 17 and 19, and the end portion is fixed to the main body case 15 by a hinge mechanism (not shown) so that it can be displaced in a fan shape. .

  The automatic document feeder 41 has a main body 43 positioned above the contact glass 17, and a document tray 45 and a paper discharge tray 47 extending from the main body 43 are positioned above the contact glass 19.

  A plurality of moving units serving as a moving unit that feeds the document 13 from the document tray 45, conveys the document 13 in a loop through the vicinity of the reading unit 27, and discharges it to the sheet discharge tray 47 in the main body 43 of the automatic document conveyance unit 41. The conveying roller 49 is arranged.

  In the main body 43, a second reading unit 51 is disposed in the vicinity of the reading unit 27. The second reading unit 51 is composed of, for example, a line sensor type CIS sensor, and has a function of directly reading a document image by contacting the back surface of the conveyed document 13 and outputting digital image data to the calculation unit 39. ing.

  The plurality of transport rollers 49 are rotationally controlled by a reading control unit 53 described later, and the reading control unit 53 is a part of the function of the main control unit 1 described above and has the following functions. Yes.

  That is, the reading control unit 53 performs reading control of the document reading unit 3 so that the document 13 is read page by page based on an instruction input from the start key 7 c or the stop 7 d, and stores read image data in the storage unit 5. In addition, it has a function of controlling the reading stop of the document 13 with respect to the document reading unit 3.

The reading control unit 53 has a function of controlling execution of reading of the document 13 with respect to the document reading unit 3 when the inspection start key 7f or 7g instructs to start a stain inspection of the document reading unit 3. When the document 13 is read and controlled, it also has a function of controlling output of image data from the first or second reading unit 37 or 51 to the main control unit 1.

  Next, the function of the main control unit 1 described above will be further described with reference to FIG.

  The main control unit 1 has a function as the image conversion unit 55 in addition to the functions described above.

That is, the image conversion unit 55 determines whether or not the read image data obtained from the document reading unit 3 is a gray document under the situation where the inspection start key 7f or 7g instructs to start the stain inspection of the document reading unit 3. When it is determined that the original is a gray original, a histogram relating to the gray original image data is created, and a threshold value for converting the image data from the gray original into a monochrome binary image is created from the histogram.

  FIG. 4 shows a histogram relating to gray original image data. For example, if the CIS sensor is in a normal state without dust or the like, the normal characteristic of the mountain shape, which is a collection of normal data, as shown by the solid line in FIG. If dust or the like is attached to a part of the line, it becomes an abnormal characteristic of a mountain shape that is a collection of abnormal data as shown by the broken line in FIG.

  The image conversion unit 55 has a function of creating a threshold value corresponding to the created histogram characteristics, and for inverting and converting individual pixels forming each line of gray original image data into a monochrome binary image. Yes. As the threshold value, for example, a value obtained by returning a certain interval from the highest peak portion (the portion with the most data) of the normal characteristic histogram is determined as the threshold value.

  The image conversion unit 55 converts the individual pixels of the image data relating to the gray original into a black and white binary image based on the created threshold value, and outputs the converted black and white binary image to the printing unit 9. It also has a function to control printing.

  For example, each pixel of gray original image data has 256 gradations between white and black, and when the normal characteristic of the solid line in FIG. 4 is obtained as a histogram, 128 gradations or more are used as threshold values. All gradation areas are converted to black pixels, and all gradation areas less than 126 gradations are converted to white pixels.

  On the other hand, when the abnormal characteristic of the broken line in FIG. 4 is obtained, the threshold value is not changed by that, and pixel conversion is performed by determining the threshold value with reference to the gradation having the largest data in the normal characteristic histogram. Thus, if white stripes are detected during reading, it can be clearly output by binarization processing.

  For this reason, when the abnormal characteristic shown by the broken line in FIG. 4 is obtained, the gradation area somewhat darker than the normal characteristic is also converted into white pixels, so that dust or the like adheres to the second reading unit 51 (CIS sensor). The vicinity of the current pixel is converted to a white pixel, and when printed, it tends to be clear.

  That is, when dust is attached to the CIS sensor, the gray portion is read in white due to the characteristics of the CIS sensor. Therefore, in the histogram in which the abnormal characteristic is seen, the abnormal characteristic portion itself has a threshold value. Since the white portion is determined and the other portions are output in black, the white lines are emphasized and clear.

FIG. 5A shows a state in which the dirt inspection data of the document reading unit 3 that has been inverted and converted into a black and white binary image in a state where dust or the like is not attached in the second reading unit 51 (CIS sensor) is printed. Fig. 6 shows a state in which the dirt inspection data of the document reading unit 3 that has been inverted and converted into a black and white binary image in a state where dust or the like is attached in the second reading unit 51 (CIS sensor) is printed.

  FIG. 5 exaggerates the vicinity of a pixel corresponding to a portion to which dust or the like is attached, and is illustrated as a white pixel region, and the white pixel region is not necessarily displayed wide (the same applies hereinafter).

  The image conversion unit 55 further reversely converts the converted black and white binary image, and controls the display of the reconverted binary image on the display panel unit 7e of the operation panel unit 7 or the printing unit 9, for example. It also has a function to output and control printing. That is, the white pixel is converted to a black pixel, and the black pixel is converted to a white pixel.

Next, the operation of the smear inspection apparatus for the document reading unit according to the present invention will be briefly described with reference to the flowchart of FIG.

  As an example, an example will be described in which the inspection gray document 13 having the gray density on both sides or the whole side of the sheet is conveyed and the gray density side is read by the second reading unit 51.

When the inspection gray document 13 is set on the document tray 45 of the automatic document feeder 41 and the inspection key 7g of the operation panel unit 7 is touched to instruct to start the stain inspection of the document reading unit 3 , the reading control is performed in step S1. Under the control of the unit 53, the roller 49 feeds the gray original 13 from the original tray 45, conveys it in a loop, and discharges it to the discharge tray 47.

  In this process, the second reading unit 51 directly reads the back image of the conveyed gray document 13 and outputs the inspection gray image to the main control unit 1 via the calculation unit 39 (document reading process).

  In the next step S2, the image conversion unit 55 creates a histogram from the read gray document image data (histogram creation process). In step S3, the image conversion unit 55 converts the gray document image data into a monochrome binary image. Is created from the histogram (threshold creation processing).

Further, in step S4, the image conversion unit 55 converts the gray original image data into a black and white binary image based on the created threshold value (image conversion processing), and the black and white binary image is read as shown in FIG. Printing is performed by the printing unit 9 as the stain inspection data of the copy (printing process).

  In the subsequent step S5, the converted black and white binary image is inverted and converted again by the image conversion unit 55, and the white pixel is converted into a black pixel and the black pixel is converted into a white pixel to be output as a binary image (replayed). Conversion processing), the binary image is output to the printing unit 9 and printed.

  Therefore, when no dust or the like is attached to the second reading unit 51, an image whose entire surface is converted to a black image is printed as shown in FIG. 5A, and dust or the like is attached to the second reading unit 51. In the state, as shown in Fig. B, an image in which a portion to which dust or the like is attached is converted into a white image, and in Fig. C, a portion to which dust or the like is attached is re-inverted from a white image to a black area. The printed image is printed.

Such a process constitutes a method for inspecting a smudge of the document reading unit of the present invention.

  Then, the service staff or user of the image forming apparatus A compares the two screens of FIGS. 5B and 5C, and even if white streaks or the like are displayed in the image, the two screens are different only in black and white and the shape and position are the same. If they are the same, it is determined that dust or the like has adhered to the reading surface of the second reading unit 51, and the reading surface of the CIS sensor is cleaned to remove dust or replace the CIS sensor itself. .

  On the other hand, if there is almost no difference between the colors of the lines formed on both screens of FIGS. 5B and 5C, it can be determined that the white lines are white lines caused by the image forming unit. For example, it is assumed that the developer aggregate is clogged between the developing roller and the developing blade that regulates the layer thickness of the developer, so that the developer is not supplied to the rotating photoreceptor and white stripes are generated. be able to.

As described above, the smear inspection device for the document reading unit according to the present invention includes the document reading unit 3 including a contact-type reading sensor that closely contacts a fed document and optically reads the surface image to acquire image data. When the read image data is a gray document, a histogram is created, and a threshold value for converting the image data from the gray document into a black and white binary image is created from the histogram, and image data from the gray document is created based on the created threshold value. Is converted into a black and white binary image and output, and a binary image obtained by re-inverting the black and white binary image is output, a converted monochrome binary image and a re-inverted binary image was and a printing section 9 for printing as soil test data of the document reading unit 3, the image conversion unit 51, and outputs the re-inverted transform the black and white binary image into a binary image feature A.

Therefore, it is possible to perform a reliable stain inspection of the document reading unit 3 easily and in a short time, and to determine whether the cause of white stripes or black stripes is caused by stains on the image reading portion or the image forming unit. In addition, the dirt inspection function of the document reading unit 3 can be mounted on the image forming apparatus A.

  In addition, since dust adhering to the CIS sensor or the like forming the second reading unit 51 is easily displayed as a white streak, it is easy for service personnel and users to determine whether the CIS sensor needs to be replaced.

In the document reading unit dirt inspection apparatus of the present invention, the document reading unit 3 is not limited to a contact type reading sensor that closely contacts a document and reads a surface image thereof, but can also be implemented by a non-contact type sensor. The type reading sensor is particularly useful because dust or the like tends to adhere to the surface.

It should be noted that the smear inspection apparatus for the document reading unit according to the present invention can be applied not only to the stain inspection detection in the second reading unit 51 but also to the stain inspection detection in the first reading unit 37. Yes.

Also, in the smear inspection apparatus for a document reading unit according to the present invention, if the histogram in the image data of the read gray document is created as a single color histogram, accurate smear inspection of the document reading unit can be performed even if the configuration and processing are simplified. Although it is possible, it is also possible to create a histogram relating to a plurality of colors in the read image data.

  By the way, the gray density of the gray document for inspection is arbitrary, but a density of about 128 gradations is preferable from the viewpoint of obtaining a clear image.

Further, if the image forming apparatus is configured by including the document reading unit stain inspection method of the present invention and the document reading unit stain inspection device described above, the same effects as those of the document reading unit stain inspection device described above can be obtained. .

1 Main control unit 3 Document reading unit 5 Storage unit 7 Operation panel unit (display unit, input unit)
7a selection key 7b numeric keypad 7c start key 7d stop key 7e display panel unit 7f, 7g inspection start key 9 printing unit 11 transmission / reception unit 13 document 15 body case 17, 19 contact glass 21 light source 23, 31, 33 mirror 25 storage unit 27 reading Unit 29 Moving section 35 Condensing lens 37 First reading section 39 Calculation section 41 Automatic document conveying section 43 Main body section 45 Document tray 47 Paper discharge tray 49 Roller 51 Second reading section 53 Reading control section 55 Image conversion section A Image Forming device B Information processing device NT Network

Claims (7)

A document reading unit that optically reads a surface image of a fed document and acquires image data;
A histogram is created when the read image data is a gray document, a threshold value for converting the image data from the gray document into a black and white binary image is created from the histogram, and the gray document is based on the created threshold value. An image conversion unit for converting and outputting the image data from a black and white binary image and outputting a binary image obtained by re-inverting the black and white binary image ;
A printing unit that prints the converted monochrome binary image and the re-inverted binary image as stain inspection data of the document reading unit ;
Document reading unit of the fouling test apparatus, characterized by comprising. 2. The apparatus for inspecting a smudge of a document reading unit according to claim 1, wherein the document reading unit includes a contact-type reading sensor that contacts the document and reads the image data. The document inspection unit dirt inspection device according to claim 1, wherein the image conversion unit creates the histogram relating to a single color in the image data of the read gray document. 4. An image forming apparatus comprising the document reading unit stain inspection apparatus according to claim 1, further comprising an image forming unit that forms an image of the read image data. A document reading process for feeding a gray document and optically reading a gray image for inspection on the surface to obtain image data;
A histogram creation process for creating a histogram from the image data relating to the read gray document;
A threshold value creating process for creating a threshold value for converting the image data relating to the gray document into a monochrome binary image from the histogram;
An image conversion process for converting the image data relating to the gray original into a black and white binary image based on the created threshold value and outputting the binary image, and outputting a binary image obtained by re-inverting the black and white binary image ;
A printing process for printing the converted black- and- white binary image and the re-inverted binary image as stain inspection data of the document reading unit at a printing unit;
A method for inspecting a smudge of a document reading section . 6. The method for inspecting a document reading unit according to claim 5, wherein the document reading process uses a contact-type reading sensor that contacts the document and reads the image data. 7. The method for inspecting a smudge of a manuscript reading unit according to claim 5, wherein the image conversion processing creates the histogram relating to a single color in the image data of the read gray manuscript.

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